The successful replacement of lost teeth by implant-fastened prosthesis would especially improve the quality of life for thousands of middle-aged and elderly edentulous patients who suffer from advanced residual ridge reduction. These individuals cannot cope with conventional prostheses and often confront the dental profession with problems that cannot readily be solved.
The edentulous and partially edentulous jaw areas are typical examples of tissue defects that cause different degrees of functional disturbances. A well-fitting prosthesis appears to be an acceptable alternative to natural teeth as long as the anatomy of the residual hard and soft tissues provides good retention for the prosthesis. Progressive loss of alveolar bone and the spreading of dental caries tends to undermine the relative stability of the prosthesis, and can create severe problems of both a functional and psychosocial nature.
Numerous dental implant systems have been designed for the prosthetic replacement of natural teeth. These systems have made use of screws, nails, blades, shanks or pins which serve as the anchor of the prosthetic attachment, and a superstructure which replaces the natural tooth. Several of the implants of this type resulted in the formation of fibrotic tissue around the implant, insufficient gingival sealing, chronic infection, and bone loss leading to the eventual failure of the implant. Improvements of the early implant systems have been made, but a totally effective implant has heretofore been unavailable.
Patent and publications describing previous implant systems include the following; Schulte, U.S. Pat. No. 4,486,178; Scantlebury et al., U.S. Pat. No. 4,531,916; Tatum, Jr., U.S. Pat. No. 4,531,915; Sandhaus, U.S. Pat. No. 4,466,796; Small, U.S. Pat. No. 4.439,152; Niznick, U.S. Pat. No. 4,431,416; Mozsary et al., U.S. Pat. No. 4,416,629; Branemark et al., U.S. Pat. No. 4,330,891; Branemark et al., U.S. Pat. No. 4,065,817; Cohen et al., U.S. Pat. No. 3,905,109; Stevens et al., U.S. Pat. No. 3,597,831; Predecki et al., J. Biomed. Mater. Res., 6: 401 (1972); Williams, J. Med. Eng. Tech., 266 (1977); Beder et al., O.S.,O.M. & O.P., 787 (1959); Branemark et al., "Osseointegrated Implants in the Treatment of the Edentulous Jawn", Scan. J. Plas. Recon. Suro., Vol. 11, Suppl. 16, (1977).
Different procedures have been advocated to implant dental prosthesis in the soft or hard tissues of the edentulous and partial edentulous jaw. However, long-term clinical follow-ups indicate that such procedures do not provide predictable long-term function. Attempts at implanting an implant by means of a regenerated fibrous tissue layer forming a simulated periodontal ligament have also been unsuccessful.
It has been stated in the bone reconstruction literature that direct implantation into living bone of load-bearing implants does not work over the long run. It has also been stated that the design of the implant surface structure is very important for success. The novel design of the present invention refutes the first of these statements and confirms the second.
During the manufacture of metal dental implants, cutting oils are used to enhance cutting tool action and to serve as a coolant for the cutting tool itself. The traditional methods of "degreasing", or removing these oils after manufacture, include rinsing in a sequence of different solvents which often leave residues of hydrocarbons on the surface of the implant. In addition a "deburring" process takes place to remove burrs and rough edges from the implant. This process may utilize either mechanical or chemical methods or both.
The implant is then rinsed, with an inorganic or organic solvent, depending on which deburring process is used. The rinsing process is employed to remove abrasive particulates, and to prevent further introduction or new contamination of the implant surface. Typically the implant surface is still contaminated with, for example: a mono-layer of hydrocarbons from the cutting oil; residual particulates from the abrasive cleaning processes; metal dust; airborn dust; residual salts; and inorganic materials.
The ultimate cleanliness of the implant is determined by the subsequent manufacturing steps. These next steps usually take place in a "clean room" facility. These may include subsequent ultrasonic rinsing with organic solvents such as freon, trichlorethylene, or various alcohols, or inorganic solvents, such as deionized or distilled water. After the rinsing process, a mono-layer of contaminants may still remain on the surface of the implant. The implant is usually packaged with these contaminants still on the surface.
Careful preparation of the implant surface by traditional cleaning before use generally reduces the quantity of contaminants. Standard sterilizing of these implants does render them free of live bacteria but tends to increase surface contamination by allowing salts to accumulate as a product of steam autoclaving. Another drawback to conventional autoclaving is the presence of deceased microorganisms on the surface of the sterilized article. The presence of such materials may interfere with the integration of the implants into the surrounding bone/tissue.
Patents describing sterilization and/or cleaning methods include; Hofmann, U.S. Pat. No. 4,524,079; Hiramoto, U.S. Pat. No. 4,464,336; Geren, U.S. Pat. No. 4,457,221; Flanagan, U.S. Pat. No. 4,391,773; Gut Boucher, U.S. Pat. No. 4,207,286; Fraser et al., U.S. Pat. No. 3,948,601 and Wesley et al., U.S. Pat. No. 3,594,115.
The method of the present invention was developed to overcome the difficulties associated with the traditional cleaning methods used for implants. The method of the present invention utilizes a plasma cleaning device to ensure the cleanliness and sterility of the entire implant system, thus assuring that the design of the present invention will have increased retentive properties as well as a good and predictable long-term prognosis.